I am adding insulation to the attic that already has insulation. I have a
heater chimney that goes through the attic. Can I use John Manville Kraft
R-19 unfaced batts to add insulation to the attic? The package says its for
wall/floor/crawl spaces. I assume it can be used for attic too. Can batts
touch heater chimney? The chimney actually has two pipes, one inside
another. The inner pipe is very thin aluminum pipe while outer pipe is
regular duct metal pipe. If batts cannot touch chimney can I use thermofiber
insulation around the chimney and keep batts 3" away from it? I think
thermofiber insulation does not burn and can touch hot objects.
You can insulate the chimney by wrapping unfaced (no paper) insulation
and secure with wire. I insulated all the attic pipes that way,
including the bathroom exhaust piping. I prefer the batts to blown-in
insulation. Do not block vents--your roof needs to "breathe."
On Sat, 8 Nov 2003 14:04:25 -0500, "Alexander Galkin"
Can't chimney get hot enough to cause fire of it touches unfaced batts? The
insulation pack I bought says to keep it at least 3" from hot objects:
chimneys, fireplaces, non-IC recessed lights, etc.
What is a heater chimney? you mean the chimney for a
furnace? Most metal chimneys are not zero clearance and
generally require a 3 inch clearance. You treat chimneys
just like you do sunken light fixtures (ones that protrude
above the ceiling). You build a ring of sheet metal around
the fixture to keep insulation or other material away from,
or in this, case the chimney to a height slight greater than
the depth of the insulation.
And no, you do not wrap any kind of insulation around the
chimney. There is no reason to and it would serve no
purpose (if it is a zero clearance chimney) and would be
dangerous if the chimney requires a 3 inch clearance.
Alexander Galkin wrote:
The chimney was used by both furnace and gas heater before I replaced the
furnace with 92% furnace that has now separate PVC pipe chimney through the
basement wall. The old metal chimney is used now only by gas heater. The
chimney consists of two pipes: light aluminum inner pipe and heavier metal
outer pipe. The chimney goes from the basement to the roof through vertical
square opening. The opening is larger then round chimney (outer metal pipe)
and warm air is sucked away from heated insulated basement and cold air is
sucked in to the basement from the attic. So this void space around the
chimney outside pipe must be closed somehow with insulation.
I'm no gas guy, but your chimney doesn't sound like a zero
clearance type so that means you need space between the
chimney and any flamable materials. I can't quite imagine
the situation you describe unless the chimney is non
standard and was never properly installed. You stop the air
flow not by insulating the chimney but by closing the
ceiling opening between the outer metal pipe and the the
"square opening" by installing the proper metal ring or wall
pass through. There should be one of these at each floor
and the roof through which the chimney passes. These are
thin galvanized metal rings that fits tightly to the outer
metal of the chimney and are 2-3 inches wider to be screwed
to the ceiling. Any store that sells gas furnaces or water
heaters should be able to provide them.
Alexander Galkin wrote:
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